The impending return home of a North Korean ship suspected of possibly carrying illicit cargo shows that efforts are working to enforce U.N. sanctions imposed against the country after its nuclear and missile tests, the chief of U.S. Naval operations said Monday.

The U.N. Security Council punished the North after its May nuclear test with a resolution and tough sanctions to clamp down on alleged trading of banned arms and weapons-related material, including authorizing searches of suspect ships.

The reclusive nation has engaged in a series of provocative acts this year and increased tensions Saturday, firing seven ballistic missiles into the ocean off its east coast in violation of three U.N. resolutions. It was the North's biggest display of missile firepower in three years.

The cargo vessel Kang Nam 1 was tracked by the U.S. Navy after it left port last month. The ship, which was believed destined for Myanmar, suddenly turned back on June 28. South Korean defense officials said it had entered North Korean waters and should reach port late Monday.

"I think that's an indication of the way the international community came together," Adm. Gary Roughead, the chief of Naval operations, said of the ship's reversal.

Speaking to reporters in Seoul, he called the monitoring of the Kang Nam I "a very effective way" of stopping proliferation, and said the Navy will continue to "conduct operations" that support the effort to sanction the North.

The Kang Nam 1, which has drawn attention in the past for suspected proliferation activities, was the first ship to be monitored under U.N. Security Council Resolution 1874 passed last month.

It bans North Korea from selling a range of arms and weapons-related material, and allows other countries to request boarding and inspection of suspected ships, though the vessels do not have to give permission.

North Korea has said it would consider interception of its ships a declaration of war.

It remains unclear, however, exactly why the Kang Nam 1 turned back or what kind of cargo was on board. Speculation has included the possibility it was carrying weapons, possibly to Myanmar. The ship has been suspected of transporting banned goods to the Southeast Asian country in the past.

Separately, Akitaka Saiki, Japan's envoy to the stalled six-nation nuclear negotiations with North Korea, said that efforts to implement the U.N. resolution will yield results.

"We expect numerous effects through consistent implementation," he told reporters in Seoul after meeting with South Korean officials.

Malaysia, meanwhile, pledged Monday to work with the United States to block the North from using the Southeast Asian nation's banks to fund any weapons deals. Foreign Minister Anifah Aman said his government "does not condone" any illegal activities.

The assurance came as Philip Goldberg, a U.S. envoy in charge of coordinating the implementation of sanctions against Pyongyang, met with Malaysian officials.

South Korean media have reported that North Korea sought payment through a bank in Malaysia for the suspected shipment of weapons to Myanmar via the Kang Nam I.

The Naval operations chief also denounced North Korea for its volley of weekend missile tests, calling them "very unhelpful and clearly counter to the desires of the international community for a peaceful and stable region."

The tests added fuel to tensions already running high after the May 25 underground nuclear test blast.

Japan's defense chief called the North's launches "a serious act of provocation" that poses a threat to his country. Defense Minister Yasukazu Hamada also said Pyongyang may fire more missiles.

The launches on July 4 — the U.S. Independence Day holiday — appeared to be a poke at Washington as it moves to enforce U.N. sanctions as well as its own against North Korea.

Despite speculation that the North might try to launch a long-range missile toward Hawaii, U.S. defense officials said there have been no imminent signs of such a move.